1. Field of the Invention
This invention relates to a process and novel compounds prepared thereby. More specifically, this invention is directed to the synthesis of piperidinyl substituted, 1,4-diaza-2-cycloalkanones by a technique involving solid-liquid phase transfer phenomena.
2. Description of the Prior Art
The increasing use of polymers in place of the more traditional types of structural materials (e.g. wood, metals, etc.) has necessitated the compounding of such polymers with a variety of stabilizers in order to enhance the ability of such polymers to withstand prolonged exposure to a variety of degradative forces. Degradation of such environmentally sensitive polymers can be caused by exposure to light, heat and/or air. Such degradation is usually manifest by either a partial or total loss of structural integrity, changes in light transmission properties, changes in color, loss or reduction in flexibility and/or resiliency, or any combination of the above phenomenon. As will be appreciated, the stabilizers which are used in conjunction with the above polymeric materials, in addition to providing protection against such degradative changes, must also be compatible with the aesthetic properties of the polymeric article and be effective at low concentrations. The economics of the marketplace dictate that these stabilizers be relatively inexpensive and capable of preparation from readily available starting materials by simple and straightforward synthesis techniques.
The diazacycloalkanones have been found to be highly effective in the stabilization of polymeric materials against the photodegradative forces of ultraviolet light. The efficacy of such materials in the UV stabilization of polymers is described in copending patent applications Ser. Nos. 835,065 now U.S. Pat. No. 4,190,571 and 835,069, now U.S. Pat. No. 4,207,228 both filed on Sept. 21, 1977; the Ser. No. 835,065 application entitled "Substituted 2-keto-1,4-Diaza Cycloalkanes and UV Light Stabilized Compositions Containing Same" and the Ser. No. 835,069 application entitled "UV Light Stabilized Compositions Containing Substituted 1,5-diazacycloalkanes and Novel Compounds". The aforementioned applications disclose methods for the preparation of compounds useful in the stabilization of UV sensitive polymer compositions. A third copending application entitled "Synthesis of 2-keto-1,4-Diazacycloalkanes" (Ser. No. 835,066 also filed Sept. 21, 1977) discloses a variety of techniques for the convenient synthesis of highly effective UV stabilizer compounds. The principal advantages of the synthesis described in the Ser. No. 835,066 application reside in the utilization of readily available starting materials, the utilization of conventional processing apparatus, the absence of hydrogen cyanide and the attendant hazards associated therewith.
In copending application Ser. No. 835,066, in the section entitled "Background of the Invention", certain references are enumerated which disclose cycloalkanes as useful UV stabilizers--see for example OLS No. 2,315,042; JAP Pat. Nos. 74-53,571 and 74-53,572; and U.S. Pat. Nos. 3,919,234; 3,920,659 and 3,928,330. Also discussed in this same section are structurally similar compounds and the limitations on the synthesis of such compounds and the analogs thereof. To the extent that this discussion is relevant to subject matter of the invention described and claimed hereinafter, it is hereby incorporated by reference in its entirety.
The prior art also discloses separate reaction of primary and secondary amines with chloroform in the presence of a phase transfer catalyst and caustic. The resultant product obtained thereby (in the case of the primary amine) was an isonitrile derivative of the primary amine; and (in the case of the secondary amine) was a foramide derivative of the secondary amine. See W. P. Weber et al, Tel.Lett 1637(1972) and J. Graefe, et al Z.Chem. 434(1974) or M. Makosza et al Rocz.Chem. 49,1627(1915) respectively. Presumably, were one to react both primary and secondary amines with chloroform under essentially the same conditions, a mixture of products would be obtained although the above references do not address this possibility.
The preparation of UV stabilizers by reaction of an appropriately substituted diamine and a suitable coreactant in the presence of a phase transfer catalyst and caustic is the subject of copending patent application, Ser. No. 916,640, filed June 19, 1978, now U.S. Pat. No. 4,167,512 in the name of John TaYuan Lai entitled, "Synthesis of 2-Keto-1,4-Diazacycloalkanes". The diamines suitable for use in such synthesis can include both primary and secondary amines. Such amines can have pendant from their .alpha.-carbons an alkyl, aryl and/or heterocyclic substituent. The provision of a specific example in the above-referenced copending application of such a hetercyclic substituted diamine is lacking.
In summary, the processes discussed in the "Background of the Invention" section of the above referenced copending application, Ser. No. 835,066 do not provide convenient techniques for the preparation of poly-substituted, 1,4-diaza-cycloalkanones. The well-known reaction of primary and secondary amines with chloroform in the presence of a phase transfer catalyst and caustic are reportedly directive for the synthesis of an isonitrile derivative of the primary amine and a formamide derivative of the secondary, respectively. The disclosure by J. T. Lai in his previously referenced copending Ser. No. 916,640 of the formation of 1,4-diaza-cycloalkanones by reaction of chloroform and "mixed" primary and secondary amines in the presence of phase transfer catalyst and caustic is thus quite unexpected. Additional effort is, however, required to realize the full scope of his discovery with respect to the synthesis of compounds have substantial stabilizer properties.